Himalayan Geology, Vol. 44 (2), 2023, pp. 64-70, Printed in India

Rock-Ice avalanche induced flash floods - Beginning of a new normal in Indian Himalayan Region

TAPAS R. MARTHA*, PRIYOM ROY, NIRMALA JAIN, K. VINOD KUMAR

Geosciences Group, National Remote Sensing Centre (NRSC), Indian Space Research Organisation (ISRO), Hyderabad - 500037, India

*Email (Corresponding author): tapas_martha@nrsc.gov.in

Abstract: Climate change and atmospheric warming have already shown their effect on the Earth's cryosphere. In the year 2021, the Indian Himalayan Region (IHR), especially the permafrost areas, witnessed few massive mass wasting phenomena which were previously unseen. On 29 October 2021, a large debris flow was observed in the upper reaches of the Kameng River in the East Kameng district of Arunachal Pradesh. The mud-laden water was carried by the Warriangbung River, a tributary to the Kameng River. This event was triggered due to a rock avalanche in the glaciated region from which the river originates. This event has a remarkable similarity to the event of 07 February 2021, wherein a massive rock and ice avalanche was triggered from the Raunthi Peak, upstream of the Rishiganga River in the NW Himalayas that caused a severe flash flood in downstream areas, resulting in significant loss of human lives and infrastructures. In this study, we correlate these two events in the NE and NW Himalayas. We have attempted to understand climatic conditions leading up to the event, the morphology of the slope and the underlying geological/structural controls, thus drawing similarities between the two events though located wide apart. We demonstrated through the comparative analysis and deductions drawn that the effects of warming and climate change are visible even in the higher reaches of the IHR. Events like Kameng and Rishiganga are now a reality and may repeat in the near future.

Keywords: Permafrost, Rock avalanche, debris flow, Satellite data, GLOF, Cloud burst